Montana’s forests are under attack: Strands of distressed, red pine trees across the state are a visible testament to the bark beetle infestation killing millions of trees. Now, officials say the beetle could be making its way to the urban forests of the Flathead.
And homeowners here must move quickly to keep their trees alive.
“Once you see the beetle on your tree, your tree is dead and it’s too late,” Pat McGlynn, a Flathead County agriculture, natural resource and community development extension agent, said. “The only way to save the tree is to take preventative action.”
Montana has lost a million acres of trees to the beetles, and in northern Colorado and southern Wyoming the situation is worse. While the beetles are not new to the region, an epidemic of this magnitude hasn’t been seen in the Mountain West in decades.
The current outbreak is being fueled by drought conditions, the homogenized age of the forest trees, and the lack of long winter cold spells that kill the beetles.
Since many of Montana’s communities are nestled within or close to pine forests, it was just a matter of time before the beetle spilled into the state’s urban environments and attacked high-value pine trees, Kevin Wanner, an assistant professor of entomology at Montana State University and extension entomologist, said.
Already about 1,000 attacked trees have been identified in the city of Great Falls, a few in the Conrad area, and even one in Shelby, with much of western Montana’s forests already affected and beetles now on the fringes of Flathead County.
“The feeling is that the Flathead is just ripe to be hit,” McGlynn said.
Beetles fly in the summer, typically from July through the end of August, seeking suitable host trees. All species of pine can be attacked; native lodgepole and ponderosa pines are preferred as well as non-native Scots pines, planted as ornamental trees. In some cases when beetle populations are high, non-host trees such as spruces and firs can also be attacked.
The black, hard-shelled beetle, the size of a fingertip, attacks trees by boring under their bark and laying eggs. When the larvae hatch under the bark, they eat the sweet, rich cambium layer that provides nutrients to the tree and inject a fungus to stop the tree from moving sap, which could drown the larvae.
“It’s like your blood flow; the cambium layer transports nutrients to the needles,” McGlynn said. “The tree dies because it’s lost its vascular system.”
To fend off the beetles, trees emit white resin, which looks like candle wax, into the beetle’s drill hole. From a distance, the stems of mass attacked trees look like they are covered in “popcorn,” Wanner said.
Sometimes the tree wins and entombs the beetle. But more often, especially in times of drought when the tree has difficulty producing resin, the tree loses.
In forests, officials say the infestation will largely have to run its course. But in urban environments there are some defenses.
Owners can nail to a tree a small packet of an “aggregator pheromone” called Verbenone, which mimics a chemical scent given off by beetles.
The first beetles attacking a tree emit an attractive chemical odor that causes scores of beetles flocking to a tree in a mass attack that helps overcome the tree’s defenses. When the tree is full, beetles begin producing Verbenone, another pheromone that acts as a sort of “no vacancy” signal. Beetles in the area get the “message” that the tree is full and they should look elsewhere.
Verbenone is non-toxic to people, pets, birds and even the beetles. It’s available at landscaping and garden centers as well as many tree farms throughout the valley, and generally costs between $15 and $30, McGlynn said.
An insecticide spray called Carbaryl is even more effective, especially for large stands of trees like the ones that shade campgrounds or parks or golf courses. But the trees need to be sprayed from the base to the height at which its circumference is less than 4 inches around. Each tree costs about $10 to $15 if hundreds are sprayed.
With either Verbenone or the insecticide, applications need to be made before the beetles fly and attack, preferably by mid-June.
If a tree is infested, it needs to be cut down. Infested trees are a risk to other nearby trees if adult beetles develop successfully, emerging the following year in greater numbers to continue attacks. Infested firewood is also a risk, since beetles can develop even after a tree is cut.
No one can say for certain that the beetle will hit here this summer. Officials say residents have to balance the risk that their trees will be attacked and killed with the cost of taking action to protect them without ever knowing whether they will be attacked.
For landowners, however, who often value their trees for everything from sentimental reasons to increased real estate values or summer shade, it’s important to take action.
“They may have had a tree in their lawn their whole adult life, and it can be gone in an afternoon,” McGlynn said. “I don’t want to be alarmist, but I don’t want people to say they wished they’d done something after it’s too late.”